Field of the Invention
The present invention relates to a method for soldering two kinds of parts, parts with leads and chip parts, on one-side printed board.
Description of the Prior Art
Recently, a surface mounting method for chip parts onto a printed board has been rapidly progressed. However, in parts with leads such as connectors, switches and the like, leads thereof to be soldered have to be inserted into lead insert holes of the printed board.
Conventional methods for soldering two kinds of parts, parts with leads and chip parts, onto one-side printed board include the following:
A. Method for First Carrying Out One-side Dip
A method which comprises inserting a lead of a part with a lead into one-side printed board to solder-dip the same, coating a cream solder on the one-side printed board to mount a chip part, and locally soldering the cream solder by soldering through a laser, a spot air reflow, or manual operation.
B. Method for First Carrying Out Reflow Soldering
A method which comprises coating a cream solder on one-side printed board and mounting a chip part, carrying out reflow soldering, inserting a lead of a part with a lead into the one-side printed board, coating the cream solder on the lead, and carrying out local reflow soldering using a spot air reflow or the like or carrying out local soldering by manual operation.
However, the aforementioned conventional methods have the following problems.
In both the methods A and B, even locally, the one-side printed board is heated twice or more and therefore the one-side printed board receives an extremely great heat stress, and the one-side printed board tends to be thermally damaged. In addition, a heat resistant printed board is very expensive.
For both the methods A and B, two or more soldering steps are required. Particularly, in case of local soldering, exclusive-use equipment has to be provided, increasing equipment cost and maintenance cost. Furthermore, manual soldering is extremely poor in workability.
The method A requires a cream solder coater for exclusive use for chip parts. The method B requires a cream solder coater for exclusive use for parts with leads. Accordingly, when a board is changed, programs for these exclusive-use cream solder coaters need be changed.
In the method A, since the solder dipping is carried out, a solder bridge tends to occur.
In the method B, when the whole one-side printed board is subjected to reflow soldering by the second soldering, heating has to be made at a temperature lower than a heating temperature used at the time of the first reflow soldering, lowering a reliability of soldering. Moreover, since theremal stress is given to the first soldered portion during the second soldering, the reliability of the first soldered portion is also degraded.